Gear Ratios on an Upper Unit

[harrydohnert]

Quick question. I am purchasing a new upper drive unit (for a 1986 Sea Ray Weekender 230 Mercruiser 230 HP.) They asked me which gear ratio my drive is. How can I tell this? Is there a standard chart, or do I need to open the existing drive and count the teeth. The person I spoke to informed me that it should be 1.5 - 1. However, she said that some boats came with options, and this could be different. Also, if anyone could explain to me what this means, that would be great as well. Thanks

 

[vipzach]

Re: Gear Ratios on an Upper Unit

The ratio may be stamped on your drive somewhere. She is probly right about the 1.50 ratio though. Most merc drives use that for the v8 and 1.98 for the 4 cyl. I don't know about the v6. If you can't find it on the drive it would be best to count the teeth, scratch one and count from there, that way you know where you started and where to stop. <br />I think the "1" in the ratio means 1 revelation of the motor to 50 revelations of the prop. I could be wrong but I think that is what it means.

 

[Haut Medoc]

Re: Gear Ratios on an Upper Unit

1:50 means that the enginem turns 1.5 times to 1 time for the prop. If its a v-8 the ratio is 1:50 to 1.......J

 

[vipzach]

Re: Gear Ratios on an Upper Unit

Damn J, if that is it then my thinking was way off! Always questioned the way I thought that ratio was. That has to be the first time I have ever been wrong about anything <br />Thanks for correcting me!

 

[Haut Medoc]

Re: Gear Ratios on an Upper Unit

If that's the first time you were wrong, then your track record is way better than mine. A good way to tell the ratio with the drive off is to put it in fwd., mark gear case, prop shaft & upper case and u-joint. Turn drive shaft 1 1/2 turns,ccw. If the marks on the prop line up, you have 1:50 gears. If you have to turn it 1 5/8, you have 1:65 gears (v-6).Two turns is 1:98. J